A drive train is a collective term representing a plurality of devices for transmitting energy generated in an engine to driving wheels, and is composed of an engine, a clutch, a transmission, a drive shaft, a propeller shaft, a differential gear, driving wheels, etc. The drive-train test system actually drives the transmission by the engine, and executes electric inertia control on a dynamometer connected to the output shaft, thereby evaluating durability performance or quality of the drive train, while giving appropriate load torque to the output shaft.
Many types of the electric inertia control employed in such a test system can set only a single inertia amount corresponding to a vehicle moment of inertia, as disclosed in, for example, Patent Document 1. This is equivalent to simulating a state where the tires of a real vehicle are always running while gripping on a road surface without slipping. The tires are likely to slip on a slippery road surface such as a snowy or icy surface that actually exists; however, the test system disclosed in Patent Document 1 is difficult to reproduce a state where the tires are slipping on such a road surface.
Patent Document 2 discloses a technique of calculating load torque, on the basis of a dynamic model of a vehicle carrying a drive train. This dynamic model includes a slip model for calculating front and back forces acting on a vehicle, on the basis of a slip ratio of tires, and vertical load acting on the vehicle; and a dynamometer generates load torque in consideration of the slip behavior of the tires.
Patent Document 1: Japanese Unexamined Patent Application, Publication No. 2009-74834
Patent Document 2: Japanese Unexamined Patent Application, Publication No. 2005-61889